ABSTRACT Our overarching goal is to better understand the role of post-translational modifications (PTMs) of cellular proteins in cancer with the underlying assumption that the enzymes that catalyze the addition or the removal of these PTMs are candidate therapeutic targets in cancer. While enzymes such as protein kinases have been extensively studied in cancer, new classes of enzymes have recently emerged as potential cancer targets. In particular, more than 100 lysine methyltransferases (KMTs) are predicted to be present in the human proteome and many are implicated in cancer etiology. However, the catalytic activity and substrate specificity for many of these enzymes remains unknown. A central hypothesis to be tested here is that uncovering the function of orphan KMTs may provide new links between protein lysine methylation signaling and cancer biology. Here we focus on the candidate KMT SETD5 (SET domain protein 5) as a potential critical regulator of tumorigenesis. SETD5 mutations are involved in the etiology of intellectual disabilities and autism spectrum disorders. SETD5 has also been implicated in influencing tumors harboring activating mutations in the KRAS oncogene, such as pancreas cancer. However, SETD5 is an orphan enzyme and knowledge of any potential endogenous substrates and the overall mode of action of this candidate enzyme in cells and in vivo is obscure. Based on preliminary observations, we hypothesize that SETD5, via regulation of chromatin dynamics, governs epigenetic programs important for normal cellular behaviors and promotes tumorigenesis. The goal of Aim 1 is to elucidate the physiologic catalytic activity of SETD5 and molecular functions of SETD5 at chromatin. We also will investigate SETD5 interacting partners and mechanisms of targeting SETD5 to the genome. In Aim 2 we characterize the role of SETD5 in tumors driven by oncogenic RAS pathway. We will test the hypothesis that SETD5 cooperates with RAS signaling to promote the unlimited expansion of cancer cells in vivo using mouse models of Pancreas Ductal Adenocarcinoma and Lung Adenocarcinoma, two most lethal human cancers in which KRAS is frequently activated. We will also investigate the tumorigenic role of SETD5 in human tissue using patient-derived xenograft pancreatic and lung cancer models and explore SETD5 as a potential therapeutic target. Finally, we focus on the mode of action of SETD5 in cancer in cells and in vivo. We will use cutting-edge gene delivery techniques to genetically modify pancreatic cancer in vivo. A long-term goal is to evaluate SETD5 as a relevant and druggable target for the treatment of lethal cancers.